Fixing ERROR_FLT_INVALID_NAME_REQUEST (0X801F0005) on Windows 10/11

You're seeing error 0X801F0005 – ERROR_FLT_INVALID_NAME_REQUEST. What's actually happening here is that the Windows Filter Manager (FltMgr.sys) received a name query from a registered minifilter driver, but the name structure was malformed — null pointer, bad Unicode string, or a buffer that doesn't match the expected format. The filter manager just slaps your hand: nope, that's not valid.

This error doesn't just pop up on its own. It usually comes from a third-party driver that registered a filter callback, then tried to query the name of a file object using FltGetFileNameInformation or similar, but passed garbage. Or the filter driver itself is corrupt or mismatched after a Windows update. I've seen it most often after an antivirus update broke its minifilter, or after installing a backup tool that hooks into the file system.

1. Broken or outdated filter driver (most common)

The number one cause: a filter driver that was installed by some software, then the software updated or was removed, but the driver registration stuck around. When Windows tries to call that driver's name-query routine, it crashes sideways and spits 0X801F0005.

The real fix is to enumerate all registered minifilters and remove the busted one. Open an admin Command Prompt. Run:

fltmc filters

You'll get a list of all active filter drivers. Look for anything that doesn't match a known Microsoft driver. Common offenders are FileCrypt (from old DiskCryptor), snapman (Acronis), or random antivirus leftovers like Symantec, Avast, McAfee filters.

If you spot something suspicious, check its details:

fltmc instances -f [FilterName]

Then forcefully remove it:

fltmc detach [FilterName] [Volume]

But that only unloads it temporarily. To kill it for good, you need to delete the driver's registry key under:

HKLM\SYSTEM\CurrentControlSet\Services\[FilterName]

Right-click the key, export it as a backup, then delete it. Reboot. The error should vanish. If you're unsure which filter is the problem, boot into Safe Mode — only Microsoft filters load there. If the error disappears in Safe Mode, you've confirmed a third-party filter is the culprit.

2. Corrupted minifilter registration after a failed update

Windows updates sometimes nuke part of a filter's registration — the Altitude, Instance, or SupportedFeatures values get corrupted. The driver loads, but its name request callback points to invalid memory. You get 0X801F0005 on the next file operation.

Check the System event log (Event Viewer → Windows Logs → System). Filter Source: FltMgr. If you see event ID 2 (filter manager detected a corrupt instance) or 1 (driver failed to register), you've hit this.

To fix it:

1. Identify the filter name from the event log.
2. Open Registry Editor, go to HKLM\SYSTEM\CurrentControlSet\Services\[FilterName]\Instances.
3. You'll see subkeys like Default Instance. Right-click the entire Instances key and export it.
4. Delete the Instances key (the whole thing).
5. Reinstall or repair the software that owns that filter.

I've seen this happen specifically with Dell Backup and Recovery and Macrium Reflect after the Windows 11 22H2 update. The update changes the NTFS volume layout just enough to break the instance registration.

3. Antivirus conflict with another filter driver

Two different antivirus products, or an antivirus plus a backup tool, try to register filters at the same altitude range. They step on each other's feet. One filter's name request call gets intercepted by the other's callback, which doesn't know what to do with it — so it returns STATUS_FLT_INVALID_NAME_REQUEST.

Check for multiple AV products. Go to Settings → Apps → Installed apps. If you see more than one antivirus, that's your smoking gun. Uninstall all but one. Reboot.

If you only have one AV but also have a cloud sync tool (OneDrive, Dropbox, Google Drive), those also register minifilters. OneDrive's CldFlt filter has been known to conflict with Bitdefender's bdFileFilter. The fix is to temporarily disable the sync tool's file system hook — you can do this by pausing sync in the app settings, or uninstalling the sync tool to test.

To see which filter is at which altitude, run:

fltmc instances

Look for altitudes that are too close (within 1000 units). Microsoft reserves ranges:

• 0–999: File system
• 1000–1999: Anti-virus
• 2000–2999: Replication
• 3000–3999: Backup
• 4000–4999: Security enhancement

If you see two filters in the same range, that's a conflict. Uninstall the one you don't need.

Quick-reference summary

In almost every case I've debugged, removing the offending filter driver fixed the error permanently. Don't waste time reinstalling Windows — just kill the broken driver.